Composite metallic bodies



Patented June 14, 1938 COMPOSITE METALLIC BODIES Clemens A. Laise,Tenafly, N. J., and Jacob Kurtz, Brooklyn, N. Y., assignors to EislerElectric Corporation, Union City,

ration of Delaware No Drawing.

N. J., a corpo- Application January 18, 1934,. Serial No. 707,106

9 Claims. (Cl. 29-182) The present invention relates to the productionof composite metal bodies such as bars, rods or wires, and to theirassociation with hard metal material. More particularly, it relates tosuch composite bodies as are adapted for-use for leadin wires orfilament supports for electric incandescent lamps and radio tubes or forgrids or grid supports for such tubes. It has special advantages whenused for lead-in wires, grids and grid supports of multigrid thermionicvalves and radio power tubes.

Such power tubes during operation generate a very considerable degree ofheat which gives rise to undesired electronic emission from metalportions of the device that interferes withthe desired electronicemission from the cathode. Particularly is this undesired emission setup in the grids and connected parts when they become overheated and thisso-called back-grid emission in a multigrid thermionic tube is a factorhighly disturbing to the smooth operation of the device. Such undesiredemission is substantially eliminated by the use of the metallic bodiesof the present invention in forming the grid structure, and thisdesirable result is due to the high heat and electrical conductivity ofsuch bodies.

In welding the leads,-supports or other connecting members to refractorymetallic members of thermionic valves and incandescent lamps, such astungsten, molybdenum or tantalum wires or rods used for conductingelectric current through hard glass envelopes and for forming a tightseal therewith, it is diflicult to ensure the formation of a strong,unitary and conductive bond. For instance, when a copper lead wire iswelded to a tungsten sealing-in member, the copper tends to becomestrongly oxidized at the temperatures required to form the union, andoften becomes so weakened and embrittled that it is unable to withstandsubsequent working, as in beading and forming in the case of radio powertubes. The result is that the joint is often broken and this causes ahigh percentage of waste, or

loss caused by defective joints. The bodies of the present invention, aswill hereinafter appear, are very readily welded and united torefractory metallic members, with the formation of a strong, flexibleand electrically conductive connection.

Other qualities rendering the composite body of the present inventionsuitable for formation into and use as a lead wire, a grid, or afilament or grid support, result from the fact that it has littletendency to oxidize, tarnish or corrode under heat, that it can withinthe invention be made reasonably rigid, and that it can be manufacturedeconomically.

The product of the present invention may in form-be a bar, rod, wire, orstrand, either by it- 7 self or integrally united with a refractorymetal.

However, in whatever particular form it may be embodied, it comprises acentral core of high electrical and thermal conductivity, and a sheathof a non-corrosive metal or metal alloy. The core may be ofcuprousmaterial, and the sheath of nickelous material.- The core may beof pure copper, but for specific purposes additions suitable for thepurpose may be added to the copper so v that the core may be a copperalloy or may contain beneficial additions in other form. The sheath,likewise, may be of pure nickel, but for specific purposes additionssuitable for such purpose may be added to the nickel so that the sheathmay be a nickel alloy or may contain beneficial additions in other form.Furthermore, the sheath may be nickelous and the, core pure cop per; orthe sheath may be pure nickel and the core cuprous, i. e., mainly copperbut alloy or havingbeneflcial additions. On the other hand, both coreand sheath may be alloy or have beneficial additions as hereinafterdescribed.

For purposes of illustration of the invention, merely, the followingexample is given of the preparation of a specific composite metal body:

Deoxidized bars of pure copper, three-quarters of an inch in diameter,as received from the mill, may be cut into lengths measuring, say, fromthirty inches to four feet; These bars are then carefully cleaned andtheir surfaces polished to free them from'oxides or other corrosiveinaterials. The copper bars are then provided with a sheath of purenickel. This may be done by forcing the copper bars into nickel sleeves,such as seamless nickel tubes having at least the same length as thecopperbars but preferably a slightly greater length. The sleeves, beforethis operation, have been carefully cleaned and their surfaces polished,both inside and outside, in a manner similar to that described above inreference to the copper bars. This results in a composite bar having acore of pure copper and a sheath of pure nickel. v

This composite bar may be then swaged in a suitable swaging machine soas to force the nickel sleeve into a very close contact with the coppercore throughout the entire length of the core, and thus to put them inposition .so that they may be welded and united in the manner which willI tremely intimate contact with the core throughout its length.

In this condition, the composite bar may be set on end on an adjustableplatform in a verticalfurnace of sufficient dimensions to accommodatethe bar, and subjected to temperatures high enough to cause the core andsleeve to fuse and weld together without melting either of them. Thistemperature is known in the art as the sweating temperature. In order toprevent the formation of oxides, this heating step may be carried outeither in vacuum or in an atmosphere of non-oxidizing gas; but when itis desired to produce a thin film of hydride on the sleeve, as

described and claimed in the: patent to Laise No.

1,989,236, dated January 29, 1935, it may be carried out in anatmosphere of dry hydrogen.

The adjustable platform in the vertical furnace should be so disposedthat only about one-half or not much more than two-thirds of thecomposite bar is subjected to the maximum temperature. After the desiredunion at this end is accomplished, the composite bar may be reversed sothat the remainder of the bar may be subjected to the sweatingtemperature (of the copper core). This sweating temperature is readilyobservable by a skilled operator. In this way the core and sleeve areuniformly welded along the entire length of the core, the alloy ofnickel and copper so formed between them serving as a brazing material.

After the constituents of the composite bar have been united, as abovedescribed; it may be removed from the furnace and rolled or swaged,which may be done either in the heat or in the cold. It is preferable,however, to swage it in the cold a number of times, with intermediateannealing as it,tends to become work hardened, until it is brought downto a diameter convenient for drawing, say three-quarters of an inch. Thedrawing may then be done in, well known manner and on well knownapparatus. As the drawing progresses, the wire or rod tends to becomework hardened and must be annealed; however, the last annealing shouldpreferably always be done in reducing gases, such as hydrogen or gasescontaining hydrogen. Thus, the composite wire, the final product in theillustrative example, will have a bright, shiny surface, which may bemetallic or may be coated with a thin hydride film. The temperature ofannealing depends upon the sizes of the bars and may properly'be, forlarge bars, about 1000" C. or, for small wires, as low as 400 C. Careshould be taken not to raise the annealing temperature sufliciently tocause the nickel or nickelous covering to become weak and brittle.

Instead of using a core of pure copper, a. core of copper alloycontaining a small percentage of beryllium may be used, the berylliumconstituting from .1% to 5% of the alloy. This does not materiallyreduce the conductivity of .the core, but hardens it somewhat. Insteadof beryllium, a small percentage of other hardening metals, such as willnot materially reduce the conductivity of the core, may be employed, theobject being to harden the core slightly and increase its tensilestrength, as well as the ultimate elongation of the composite wire. Thiselongation'should be from 10% to i. e., the core should be capable ofelongation to this extent before rupture.

The sheath may, as previously indicated, be of composite construction.It may contain any non-corrosive metal or alloy such as nickel orcobalt, or nickel alloys of manganese, titanium, tantalum, platinum,gold, silver, etc., in the pro- The rod or wire, or a plurality ofwires, twisted into a cable, may with great facility be welded torefractory metal such as tungsten, rhenium, molybdenum, tantalum, or thelike,--for instance, to other parts of the tubes or lamps. Metals ofthis nature are often used to carry current through the press of suchtubes or lamps, and to form a tight seal with the hard glass envelopethereof. A heat-conducting connection to such members is of distinctadvantage, and a wire or cable exemplifying the metallic body of thepresent invention is very well adapted to be united with such hard metalmembers. When such a weld is adopted, there results a strong, flexibleconnection between the members, the composite body readily forming analloy of lower melting point than either of its constituents, on thetungsten or molybdenum during the welding or uniting operation. Thewelding may be accomplished in any desired manner although I prefer tocontact the members and spot-weld them. Thus, the novel metallic body ofthe present invention readily fuses and alloys with the tungsten ormolybdenum, etc., of the refractory metallic members and makes a perfectunion. The reason for this is because oxidation and resultingembrittling of the joint, which occurs when copper and similar metalsare used to unite and weld with tungsten or molybdenum, are eliminated.Ordinary wire or strands of copper and the like are so weakened throughheating and oxidation that they break away from the refractory metal andare not capable of withstanding beading and forming as is the case inmaking power tubes. With the welded union of the present invention,therefore, a great saving is achieved because of the reduction of lossfrom imperfect and embrittled products of this nature.

The sheath or covering of nickelous material may constitute from 10% to50% of the weight of the composite bar, rod or wire, although for radiopurposes the proportion is preferably 20% to 35% of the weight of thebody.

Instead of fitting a sleeve of nickel around the cuprous core, coveringof the core may be performed in other ways. For instance, the core maybe coated by spraying the molten nickel or metal on to the same. In somecircumstances it may be convenient actually to melt the copper or copperalloy in a seamless nickel tube closed at one end. It is alsocontemplated, if desired, to unite the-cuprous core to the outer sleeveby means of an intermediate layer of a brazing alloy such as brass orsilver solder.

As previously indicated, the invention is also useful for producing awire from which to form grids for thermionic valves for filaments inelectric lamps. For such applications it is necessary to use wire whichis non-corrosive, reasonably stifi and of high heat and electricalconductivity. The improved wire in accordance with the invention has amuch greater heat conductivity than molybdenum nickel and nichrome wiresused heretofore in this connection. Hence the improved wire willdissipate excess heat in thermionic valves and electric lamps muchquicker 'proved dissipation of heat in such apparatus,

which results from forming the grids from the improved wire, lowers theoperating temperature of the grids suiliciently to ensure thesubstantial absence of back-grid emission. Furthermore, the improvedcomposite wire may be produced at a much lower cost than grid wires ofmolybdenum and molybdenum and tungsten alloys.

The composite metallic bodies of the invention may be used forheat-dissipating and non-corrosive purposes other than those alluded toabove; for instance, they may be formed with wire and woven into meshedmaterial for use as automobile brake linings. The bodies may also beused to advantage where their non-corrosive and electrically conductivequalities are desired to be utilized, as in the form of a stranded cablefor use as storage battery cables.

In the main, these composite metallic bodies manifest their advantagesand are best suited for use in the art of electricity, e. g.,conductors. electrodes, and supports, and they, therefore, will beidentified in the appended claims as electrical assemblies.

What we claim is:

l. A composite metallic body comprising a cuprous core and a covering ofnickel metal, said covering constituting from 10% to of the weight ofthe body.

2. A composite metallic body comprising a cuprous core and a covering ofnickel metal, said covering constituting from 20% to 35% of the weightof the body.

3. A composite metallic body comprising a core of high electrical andheat conductivity and a covering of a metallic material non-corrosiveunder normal conditions of oxidation and hydration, said coveringconstituting from 10% to 50% of the weight of the metallic body andadapted to form with said core a welding material readily covering of a.metallic material non-corrosive under normal conditions of oxidation andhydration, said covering constituting from 20% to 35% of the weight ofthe metallic body and adapted to form an alloy with said core forwelding with refractory metals.

5. A composite metallic body comprising a core of high electrical andheat conductivity and a covering of a non-corrosive metallic materialconstituting from 10% to 50% of the ,weight of the metallic body andsaid covering containing a metal hydride, said body adapted to form analloy for welding with refractory metals.

6. A composite wire consisting of a copper core and a nickel sheath, thesheath constituting from 10-50% of the weight of the wire.

'7. A composite wire consisting of a copper core and a nickel sheath,the sheath constituting from 20-35% of the weight of the wire.

8. A composite rod consisting of a copper core and a nickel sheath, thesheath constituting from 10-50% of the weight of the rod.

9. A composite rod consisting of a copper core and a nickel sheath, thesheath constituting from 20-35% of the weight of the rod.

CLEMENS A. JACOB

